Experimental Evaluation of the Blackbody Radiation Shift in the Cesium Atomic Fountain Clock

Fan Yang,Hui Zhang,Yang Bai,Qiang Hao,Shougang Zhang,Junru Shi,Sichen Fan,Yong Guan,Jun Ruan,Dandan Liu,Xinliang Wang

doi:10.3390/app12010510

Abstract

The cesium atomic fountain clock is the world’s most accurate microwave atomic clock. The uncertainty of blackbody radiation (BBR) shift accounts for an increasingly large percentage of the uncertainty associated with fountain clocks and has become a key factor in the performance of fountain clocks. The uncertainty of BBR shift can be reduced by improving the system environment temperature. This study examined the mechanism by which the BBR shift of the transition frequency between the two hyperfine energy levels of the 133Cs ground state is generated and the calculation method for the BBR shift in the atomic fountain. Methods used to reduce the uncertainty of BBR shift were also examined. A fountain system structure with uniform temperature and good heat preservation was designed, and related technologies, such as that for measuring the temperature of the cesium fountain system, were studied. The results of 20 days of measurements, in combination with computer simulation results, showed that the temperature uncertainty of the atomic action zone is 0.12 °C and that the resulting uncertainty of BBR shift is 2.4 × 10−17.

Highlights

Academic Editor: Baptiste BattelierThe cesium atomic fountain clock is the most advanced microwave frequency standard in the world and is used for many purposes, such as frequency measurement, international atomic time calibration [1], high-precision spectroscopy [2], testing basic physical theories [3], and measuring basic physical constants [4]
When the frequency uncertainty of a fountain clock reaches an order of magnitude of 10−16, the influence of the blackbody radiation (BBR) shift on the uncertainty of the fountain clock becomes a key factor in the further improvement of the clock performance [5,6]
The results showed that the temperature uncertainty of the atomic flight zone was less than 0.12 ◦ C, and the resulting uncertainty of BBR shift was 2.4 × 10−17, which corresponds to the international advanced level [7,8,9,12]

Summary

Introduction

The cesium atomic fountain clock is the most advanced microwave frequency standard in the world and is used for many purposes, such as frequency measurement, international atomic time calibration [1], high-precision spectroscopy [2], testing basic physical theories [3], and measuring basic physical constants [4]. Designed a copper vacuum pipeline for the atomic flight zone in its cesium fountain clock. Three T-type thermocouples are placed along the length of the water cooling jacket to monitor the temperature, and the resulting uncertainty of the BBR shift in the cesium fountain clock is 7.0 × 10−17 [9]. Another method is to lower the temperature of the atomic flight zone. BBR refers to the phenomenon by which objects at certain temperatures radiate electromagnetic waves This radiation field has a broad frequency spectrum and can cause changes in the atomic energy levels. 3,0 .frequency magnetic field to the AC the isotropic magnetic field induction energy contributes to the AC Zeeman frequency

Bν shift:

Constant Temperature Structure Design of Fountain System

Physical system temperature temperature measurement:

Temperature Measurement Research of Atomic Flight Zone

Temperature Simulation and Analysis

Conclusions